Below, a few prior art entertainment systems are described. Additional devices usage of these systems may be obtained and described from the identified references below.
U.S. Pat. No. 6,778,073 discloses a vehicle audio system includes a wireless audio sensor configured to wirelessly detect different portable audio sources brought into the vehicle. Audio output devices are located in the vehicle for outputting audio signals from the different audio sources. A processor selectively connects the different audio sources to the different audio output devices. In another aspect, the audio system includes object sensors that detect objects located outside the vehicle. The processor generates warning signals that are output from the different audio output devices according to where the objects are detected by the object sensors.
U.S. Patent Application No. 2011/0014871 discloses a wireless communication terminal comprising a network communication unit, short distance wireless communication unit, an input unit and a control unit. The network communication unit transmits radio signals to communication network via a base station. The short distance wireless communication unit transmits radio signals to and from an external device. The short distance wireless communication unit establishes a voice link between the wireless communication terminal and the external device to transmit sound data. The input unit inputs a volume control instruction. The control unit controls the short distance wireless communication unit to send a signal based on the volume control instruction if the voice channel is established between the wireless communication terminal and the external device.
U.S. Pat. No. 7,251,330 discloses a content playback system for sharing content possessed by many users who each hold a token of encrypted content, the content playback system including a playback requesting apparatus which holds a token and which requests the playback of the encrypted content, and a temporary playback apparatus for performing the playback of the encrypted content in response to a playback request of the content. The temporary playback apparatus transmits a token sending request in a form in which an identifier of the content and a digital signature are attached. The playback requesting apparatus returns the token to the temporary playback apparatus only when an authentication procedure for the digital signature is successful.